<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>时间选择器</title>
</head>
<style>
    * {
        margin: 0;
        padding: 0;
        list-style: none;
    }

    .datepicker {
        display: inline-block;
        position: relative;
        width: 280px;
        height: 30px;
    }

    .datepicker-box {
        width: 280px;
        height: 320px;
        position: absolute;
        left: 0;
        top: 30px;
        /* display: none; */
    }

    .datepicker-box .datepicker-header {
        width: 280px;
        height: 40px;
        display: flex;
    }

    .datepicker-header .header-prev {
        flex: 1;
    }

    .datepicker-header .header-next {
        flex: 1;
    }

    .datepicker-header .header-content {
        flex: 3;
    }

    .datepicker-header div {
        text-align: center;
        line-height: 40px;
        height: 40px;
        background-color: black;
        color: burlywood;
    }

    .datepicker-title {
        width: 280px;
        height: 40px;
    }

    .datepicker-title .item,
    .datepicke-content .item {
        float: left;
        width: 40px;
        height: 40px;
        text-align: center;
        line-height: 40px;
        background-color: black;
        color: blanchedalmond;
    }
</style>

<body>
    开始时间
    <div class="datepicker">
        <input id="start" />
        <div class="datepicker-box">
            <div class="datepicker-header">
                <div class="header-prev">上</div>
                <div class="header-content">2021-10</div>
                <div class="header-next">下</div>
            </div>
            <div class="datepicker-title">
                <div class="item">一</div>
                <div class="item">二</div>
                <div class="item">三</div>
                <div class="item">四</div>
                <div class="item">五</div>
                <div class="item">六</div>
                <div class="item">日</div>
            </div>

            <div class="datepicke-content">
                <div class="item"></div>

            </div>

        </div>
    </div>
</body>
<script>
    
</script>
</html>